This invention relates to a method of collapsing an appliance to be implanted which belongs to a field of medical devices (wherein the appliance collapsible for insertion into a human organ and capable of resilient restoration will be referred to as xe2x80x9can appliance to be implantedxe2x80x9d in this specification and claims) and the appliance to be implanted.
With a recent progress of medical techniques, a technique enabling transvascular use of a variety of appliances such as artificial blood vessels without ventrotomy has reached a clinical stage. Specific examples of such a technique include a method of transferring and fixing an artificial blood vessel using a catheter which has been invented by the inventor of present claimed invention and disclosed in the paper (for example, PCT/JP96/01347 which has been published with International Publication No. WO96/36387). This method includes; inserting a catheter into a human body through an inguinal artery to position a front end thereof near an affected portion in which an aneurysm or the like is present, inserting a tubular artificial blood vessel provided with collapsible/restorable elasticity into the catheter in a collapsed condition, transporting the artificial blood vessel to a predetermined location near the affected portion by the use of a transporting device or a hauling device, and releasing the artificial blood vessel from the catheter at the location, thereby to position the artificial blood vessel in an affected blood vessel having the aneurysm.
In the above-described document, the appliance to be implanted comprises a front end wire ring, a rear end wire ring arranged facing to the front end wire ring, a tubular cover which connects the front end wire ring and the rear end wire ring, and a plurality of intermediate wire rings spaced apart from each other between the front end wire ring and the rear end wire ring in which the circumference of the front end wire ring is equally divided into four or an even number over four segments with dividing points between the segments and hooking portions are formed for a front pull string to be passed through at every other dividing point between the segments, the front end wire ring is folded into a wavy shape with the dividing points where the hooking portion is provided forming a forwardly directed peak and the other dividing points forming a bottom of a forwardly directed valley and the intermediate wire rings and the rear end wire ring are folded into a wavy shape having the same phase as that of the front end wire ring.
With the method of collapsing the artificial blood vessel, a number of the hooking portions for a front pull string equals to a number of peaks when collapsed. In the artificial blood vessel of the above arrangement if a number of the hooking portions is set to be small, for example, two, pulling force is difficult to be transferred uniformly to the artificial blood vessel when the artificial blood vessel is released from the catheter, which makes the artificial blood vessel tilt easily. As a result, it becomes difficult to release the artificial blood vessel with the front end wire ring opening at right angles to an axis of the artificial blood vessel. In addition, the artificial blood vessel might not be able to be restored into an appropriate original shape after released from the catheter due to a possible habit of the wire rings because a pulling force is concentrated on the peaks of the wire rings while the artificial blood vessel is transported in the catheter.
In order to solve the above problems, it can be conceived that the number of hooking portions is increased. However, in this arrangement the number of the peaks also increases inevitably, resulting in being bulky when collapsed. As a result, it is difficult to transport thus arranged artificial blood vessel stably without causing bulky when collapsed. In addition, it is impossible to get rid of stress concentration fully because the artificial blood vessel is hauled at a portion of the peak.
In order to solve the above problems, in collapsing an appliance to be implanted comprising a front end wire ring, a rear end wire ring arranged facing to the front end wire ring, a tubular cover which connects the front end wire ring and the rear end wire ring, and an intermediate wire ring arranged between the front end wire ring and the rear end wire ring, in which each of the wire rings is given flexibly foldable elasticity, the present claimed invention is characterized by that circumference of a front end portion of the appliance to be implanted is equally divided into four or an even number over four segments with dividing points between the segments, a front hooking portion for hauling the appliance to be implanted is formed at midpoints between each adjacent two of the dividing points, the front end portion is collapsed into a wavy shape with every other dividing point forming a forwardly directed peak and other dividing point forming a bottom of a forwardly directed valley and the intermediate wire ring and the rear end wire ring are collapsed into a wavy shape having generally the same phase as that of the front end portion.
In order not to prevent the appliance to be implanted from being collapsed by the intermediate wire ring it is preferable that the appliance to be implanted is collapsed in a condition that the intermediate wire ring is fixed to the tubular cover at positions which generally correspond to the positions where the front hooking portions are provided.
In order to keep the collapsed condition for sure it is preferable that the appliance to be implanted is kept in a collapsed condition by a retaining means and the collapsed appliance to be implanted is restored into an original shape by releasing the retaining means at a target position.
In order to make it possible to release the appliance to be implanted from the collapsed condition in a remote place without fail it is preferable that the retaining means comprises a string which is wound around the collapsed appliance to be implanted and which has a loop at one portion thereof and a retaining rod which passes through the loop of the string, the appliance to be implanted is kept in the collapsed condition by passing the retaining rod through the loop of the string and the collapsed condition by means of the string is released by drawing the retaining rod out of the loop.
In case a rear hooking portion for hauling the appliance to be implanted is provided at a position which has generally the same phase as that of a position where a front hooking portion is provided on a rear end portion of the appliance to be implanted, it is preferable that the appliance to be implanted is collapsed so that the rear hooking portion locates at midpoints between the forwardly directed peaks and the bottoms of forwardly directed valleys when the rear end portion is collapsed to have generally the same phase as that of the front end portion.
In case a rear hooking portion for hauling the appliance to be implanted is provided at every other position which has generally the same phase as that of the dividing points on a rear end portion of the appliance to be implanted, it is preferable that the appliance to be implanted is collapsed so that the rear hooking portion locates at the bottoms of the forwardly directed valleys of the rear end portion when the rear end portion is collapsed to have generally the same phase as that of the front end portion.
In order to collapse the appliance to be implanted into a small size with ease it is effective if the front and rear end wire rings are connected with the tubular cover through a film member so that an annular gap at least formed between each of the front and rear end wire rings and the tubular cover is liquid-tightly sealed and the appliance to be implanted is collapsed with each of the front and rear end wire rings making a back and forth movement relative to the tubular cover within a certain range.
In order to secure an appropriate function of transportation and travel as well as to keep a collapsed condition in compact as much as possible it is preferable that a number of the dividing point is four.
A preferable example of the appliance to be implanted may be represented by an artificial blood vessel.
A form of an appliance to be implanted for realizing the above method of collapsing the appliance to be implanted may be represented by the appliance to be implanted which has an arrangement that each of the wire rings is collapsed into a wavy shape with having forwardly directed peaks and bottoms of forwardly directed valleys continuously and alternatively and which can be transported by being hauled forward with this condition kept wherein a front hooking portion for hauling the appliance to be implanted is provided at a general-midpoint between the peak and the bottom of the adjacent valley on the front end portion of the appliance to be implanted.
More concretely, it may be represented by an appliance to be implanted having an arrangement that front hooking portions for hauling the appliance to be implanted are provided at positions each of which locates at a general-midpoint between a dividing point and an adjacent dividing point wherein the dividing points divide the circumference of the front end portion into four segments and that rear hooking portions for hauling the appliance to be implanted are provided at four positions on the rear end portion of the appliance to be implanted wherein each of the four positions has the same phase as that of the front hooking portion, or an appliance to be implanted having an arrangement that front hooking portions for hauling the appliance to be implanted are provided at positions each of which locates at a general-midpoint between a dividing point and an adjacent dividing point wherein the dividing points divide the circumference of the front end portion into four segments and that rear hooking portions for hauling the appliance to be implanted are provided at two positions on circumference of the rear end portion of the appliance to be implanted or adjacent the two positions wherein each of the two positions locates at the bottoms of forwardly directed valleys.
In order to facilitate use at a site where appliance to be implanted is actually used it is preferable that front hooking portions for hauling the appliance to be implanted are provided at positions each of which locates at a general-midpoint between a dividing point and an adjacent dividing point wherein the dividing points divide the circumference of the front end portion into four segments and a transporting device wherein a wire passes into a tube and a front portion of the wire is selectively exposed through an opening portion provided on the tube is detachably be attached to the front hooking portions by engaging the tube and the wire.
With the same purpose, it is preferable that front hooking portions for hauling the appliance to be implanted are provided at positions each of which locates at a general-midpoint between a dividing point and an adjacent dividing point wherein the dividing points divide the circumference of the front end portion into an even number over four segments and the front portion is collapsed into a wavy shape with every other dividing point forming a forwardly directed peak and the adjacent dividing point forming a bottom of a forwardly directed valley and other intermediate wire ring and the rear end wire ring are collapsed into a wavy shape having the same phase as that of the front end portion and the appliance to be implanted is kept in a collapsed condition by a releasable retaining means with the above condition kept.
A concrete embodiment of the retaining means may be represented by a retaining means which is so arranged to release the appliance to be implanted from a collapsed condition by drawing a part of the retaining means out of the retaining means.
More concretely, it is effective if the retaining means comprises a string having a loop at one portion thereof and a retaining rod which is to pass through the loop of the string and the appliance to be implanted is kept in a collapsed condition with the retaining rod passing through the loop of the string and the appliance to be implanted is released from the collapsed condition by drawing the retaining rod out of the loop.
In this case also it is preferable that the intermediate wire ring is fixed to the tubular cover at positions which generally correspond to the positions where the front hooking portions are provided in order to effectively prevent the appliance to be implanted from being bulky.
A concrete position for providing the rear hooking portions for hauling the appliance to be implanted may be represented by positions which have the same phase as that of the front hooking portion provided at the front end portion of the appliance to be implanted on the rear end portion of the appliance to be implanted so as to make a number of the rear hooking portion equal to that of the front hooking portion, or every other positions which have the same phase as that of the front hooking portion provided at the front end portion of the appliance to be implanted on the rear end portion of the appliance to be implanted so as to make a number of the rear hooking portion half the number of the front hooking portion.
In this case also for collapsing the appliance to be implanted into a small size easily it is preferable that at least each of the front end wire ring and the rear end wire ring is connected with the tubular cover through a film member so that each of the front end wire ring and the rear end wire ring can make a back and forth movement relative to the tubular cover within a certain range and an annular gap formed between the front end wire ring and the tubular cover or between the rear end wire ring and the tubular cover is liquid-tightly sealed.
A preferable embodiment may be represented by that a number of the dividing point is four.
The present claimed invention is effective if applied to an artificial blood vessel which is one of the appliances to be implanted.
With the method of collapsing the appliance to be implanted in accordance with the present claimed invention, if a number of the front hooking portion is increased, the appliance to be implanted can be collapsed without increasing a number of the dividing point, in other words, a number of the peak or the bottom of the valley which is formed when collapsed. More specifically, if the appliance to be implanted is collapsed in a condition that the front hooking portion locates at a position of the peak, a number of the dividing point is required to be twice as many as the number of the front hooking portion. However, in accordance with the present claimed invention, the appliance to be implanted can be collapsed appropriately even though the number of the dividing point is equal to the number of the hooking portion. As a result, the appliance to be implanted can be kept in a collapsed condition so as not to be bulky without increasing a number of the dividing point. Further, with this arrangement, the appliance to be implanted can be hauled at a relatively straight portion between the peak and the valley of the front end wire ring locating at the front end portion of the appliance to be implanted. As a result, there is no chance that force is applied to a bent portion locally, which effectively avoids inconvenience that the wire rings are prevented from being restored into an appropriate original shape due to a possible habit of the wire rings because force is concentrated on the bent portion.
In addition, if the intermediate wire ring is fixed to the tubular cover at position which generally correspond to the positions where the front hooking portions are provided, when the intermediate wire ring is collapsed into a wavy shape having a peak and a valley, a generally mid-position between the peak and the valley of the intermediate wire ring, in other word a position which hardly move toward front and rear is fixed to the tubular cover. As a result, the appliance to be implanted can be transformed without dragging the tubular cover, resulting in a compact collapsed state of the appliance to be implanted.
Further, with the method of collapsing the appliance to be implanted in accordance with the invention, the appliance is hauled forward at the front hooking portions provided at generally mid-positions between the peak and the valley. However, the appliance does not tend to transform into a bulky shape that the mid-position where the front hooking portion is provided becomes a peak so as to double the number of the dividing points if the appliance to be implanted is once contained in the catheter in a collapsed condition. If, however, the appliance to be implanted is collapsed into a small size by the above retaining means, the appliance to be implanted can be prevented from being deformed during transportation without fail. If the appliance to be implanted is collapsed in advance by the use of the retaining means, there will be no need of collapsing the appliance to be implanted every time it is used, which makes it possible to introduce the appliance to be implanted into the catheter speedy.
In this case, if the retaining means comprises a string and a retaining rod wherein a retaining condition by means of the string can be released by a step of drawing the retaining rod, the appliance to be implanted can surely be operated to release the retaining means at a remote place after transported into a target position.
In addition, in case that the appliance to be implanted has a rear hooking portion for hauling the appliance to be implanted at a position which has generally the same phase as that of the front hooking portion on a rear end portion of the appliance to be implanted and the appliance to be implanted is collapsed so that the rear hooking portion locates at midpoints between the forwardly directed peaks and the bottoms of forwardly directed valleys, force can be applied uniformly to the rear end portion as well as the front end portion of the appliance to be implanted. As a result, the appliance to be implanted can be hauled appropriately.
In case that the appliance to be implanted has a rear hooking portion for hauling the appliance to be implanted at every other position which has generally the same phase as that of the dividing points on a rear end portion of the appliance to be implanted and the appliance to be implanted is collapsed so that the rear hooking portion locates at the bottoms of the forwardly directed valleys of the rear end portion, it is possible to haul the appliance to be implanted with occupying an opening of the rear end portion of the appliance to be implanted as less as possible. As a result, enough space can be secured for a transporting device which will be described later or other devices to be inserted into the appliance to be implanted from a rear end thereof.
If the front and rear end wire rings are connected with the tubular cover through a film member so that an annular gap formed between each of the front and rear end wire rings and the tubular cover is liquid-tightly sealed, a bent portion of the front and rear end wire rings can make a back and forth movement relative to the tubular cover. As a result, the tubular cover does not have to follow transformation of the front and rear end wire rings completely, thereby to make a range in which the tubular cover is bent smaller than that of the wire rings and to avoid forming a big wrinkle when folded. As a result of this, the appliance to be implanted can be collapsed in a compact state. In addition, since the tubular cover is not dragged much when released at a target position in a blood vessel, it can be restored into an original shape smoothly.
If a number of the dividing point is set to be four, the front hooking portions are arranged at four points each makes a right angle. As a result, the appliance to be implanted can be transported without applying force to the circumference of the front end portion thereof locally and can keep in an appropriate posture without inconvenience that the front end wire ring is tilted due to blood flow when released from the catheter at the target.
The above method can be extremely useful if applied to an artificial blood vessel which is required to be restored into an original shape at an affected portion in which an aneurysm or the like is present after being transported through a catheter in a collapsed compact condition.
If the appliance to be implanted is made to be collapsible by the above method of collapsing an appliance to be implanted, above-mentioned various effects can be produced.
In addition, if a transporting device comprising a tube and a wire is detachably attached to the appliance to be implanted, it can save time and effort for a user to set the transporting device on the appliance to be implanted every time the user uses the appliance to be implanted, which makes it possible to insert the appliance to be implanted into a catheter on the spot by the use of the transporting device.